Oxidative stress defence responses of wheat (Triticum aestivum L.) and chilli (Capsicum annum L.) cultivars grown under textile effluent fertilization

Oxidative stress is complex physiological phenomenon that accompanies virtually in all stresses including either the deficiency or the surplus of micronutrients in the soil. In response to reactive oxygen species (ROS) generation, plants use a range of mechanisms to minimize the toxicity and protect cell membranes from damage. There are known reports indicating that effluents from the textile industry can serve as a micronutrient supplier under otherwise limited conditions. However, the addition of these effluents may cause toxicity to plants due to the presence of some non-essential heavy metals and persistent compounds if supplied in excess. A mesocosm study was conducted with wheat (Triticum aestivum L) and chilli (Capsicum annum L) cultivars grown under textile effluent fertilization to evaluate the accumulation of malondialdehyde (MDA) and H2O2, and the enzymatic and non-enzymatic antioxidative defences developed against this stress. Our findings indicated that the accumulation of MDA and H2O2 were mainly stimulated in control plants (0% textile effluent) followed by 60% concentration of textile effluent fertilization. Plants counteract oxidative stress by increasing both enzymatic (Superoxide dismutase, SOD; catalase, CAT; peroxidase, POX; ascorbate peroxidase, APX; glutathione reductase, GR) and non-enzymatic (phenolic compounds, flavonoids and ascorbic acid) antioxidants significantly. The activities of major antioxidants were promoted by higher concentrations of textile effluents. In addition, low antioxidative defences against damage caused by oxidative stress to the controls were evident by yield loss and deteriorated product quality. Compared to the chilli cultivars, MDA and H2O2 were higher in wheat cultivars; at the same time activities of antioxidants were also higher in wheat cultivars. The results of this study showed that the application of textile effluents supplied plant nutrients which improved antioxidative defences by regulating the enzymatic and non-enzymatic antioxidative mechanisms while the nutrient deprived condition prevailed.